<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

        body {
            margin: 0px;
            padding: 0px;
        }
        .diyi {
            width: 800px;
            height: 60px;
            border: 1px solid;
            background-color: antiquewhite;
        }
        li{
            list-style:none;
            
            width: 100px;
            height: 60px; 
            float: left;
            margin-left: 45px;
            text-align: center;
            line-height:55px;
        }
        ul{
            margin-block-start: 0px;
            margin-block-end: 0px;
            padding-inline-start: 0px;
            
        }
        li:hover{
            color: #cea76e;
            transition: all 0.5s ease-in-out;
            position: relative;
        }
        
        div>ul>li>div>ul>li{
            margin-block-start: 0px;
            margin-block-end: 0px;
            margin-inline-start: 0px;
            margin-inline-end: 0px;
            padding-inline-start: 0px;
        }
        .yinchang {
            display: none;

            padding-top: 5px;
            margin-top: 0px;
            padding-bottom: 0px; 
            margin-bottom: 0px;
        }
        .aaa{
            position:relative;
        }
        .aaa:hover .yinchang{ /*span 标签仅在 :hover 状态时显示*/
            display:block;
            visibility: visible;
            opacity: 1;
            background: #333;
            box-shadow: 1px 1px 7px rgba(0, 0, 0, .5);
            animation-name: swingdown;
            animation-duration: 1s;
            animation-timing-function: ease;
        }
    </style>
</head>
<body>
    <div class="diyi">
        <ul>
            <li class="aaa">一号左右
                <div>
                    <ul>
                        <li class="yinchang"></li>
                        <li class="yinchang"></li>
                        <li class="yinchang"></li>
                        <li class="yinchang"></li>
                    </ul>
                </div>
            </li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
            <li>5</li>
        </ul>
        
    </div>
    <!-- 参考 -->
    <!-- http://www.cssmoban.com/preview/index.html?url=http://zly_20201117_07.demo.mxyhn.xyz/&id=13209&tid=20209539500826 -->
     <div>
        <a href="2021.11.12足球场.html">足球场</a>
    </div>
    <div>
        <a href="2021119.html">div布局</a>
    </div>
    <div>
        <a href="gezi.html">8*8</a>
    </div> 
    <div>
        <a href="form.html">form表单</a>
    </div> 
</body>
</html>